Conventional set-top boxes already deployed in the field comply with some type of modulation and error correction standards. As new modulation and coding schemes are being introduced, backward compatibility in the transmitted signal cannot be preserved at all times. Incompatibility often forces service operators to swap out large numbers of set-top boxes in order to allow the users to receive the new signal format. Such swap outs are costly and undesirable.
Some conventional approaches to set-top box compatibility implement backwards-compatible modulation, such as hierarchical modulation. One such approach has been proposed DVB-S2 for satellite transmission. However, backwards compatibility is only a partial solution to the problem and can have additional drawbacks. In particular, the DVB proposal provides sub-optimal data transmission since some loss is introduced. The additional loss has resulted in other operators avoiding the implementation of the proposal.
It would be desirable to implement a transmodulator that may be installed in the signal path before the set-top box to convert an advanced data signal to a legacy data signal for set-top boxes that are not compliant with the advanced data signal. It would also be desirable to implement baseband video signaling for a set-top box local loop connection to provide continuous communication with the transmodulator unit.